A common classroom activity for demonstrating how fossils form is to make a mold in plaster and then a cast in plaster from the mold. We include here a list of several websites where you can find plaster molds and casts activities, as well as the same exercise using white glue and candle wax in case you don't want to mess around with plaster. There are also activities for demonstrating how petrification and carbonization work, as well as for understanding fossil trackways.